One of the most terrible avalanches in the history of mankind descended from Mount Huascaran (Peru) about half a century ago: after an earthquake, a huge mass of snow broke off its slopes and rushed down at a speed exceeding three hundred kilometers per hour. On the way, she broke off part of the underlying glacier, and also carried away sand, rubble, and blocks.

On the way of the snow stream there was also a lake, the water from which after great strength the impact splashed out and, adding water to the rushing mass, formed a mudflow. The avalanche stopped only after it covered a distance of seventeen kilometers and completely demolished the village of Ranairka and the city of Yungay, killing about twenty thousand people: only a few hundred local residents managed to escape.

An avalanche is formed by snow, ice and rocks after they begin to slide down steep mountain slopes at an ever-increasing speed (from 20 to 1000 m/s), capturing new portions of snow and ice, increasing their volume. Considering that the force of the impact of the elements often amounts to tens of tons per square meter, the avalanche sweeps away everything in its path. It stops only at the bottom, reaching the gentle sections of the slope or being at the bottom of the valley.

Avalanches form only in those parts of the mountain where forests do not grow, the trees of which could slow down and prevent the snow from gaining the required speed.

The snow cover begins to move after the thickness of freshly fallen snow begins to be at least thirty centimeters (or the old layer exceeds seventy), and the steepness of the mountain slope ranges from fifteen to forty-five degrees. If the layer of fresh snow is about half a meter, the probability of snow melting in 10-12 hours is incredibly high.

It is impossible not to mention the role of old snow in the formation of avalanches in the mountains. It forms an underlying surface, which allows freshly fallen precipitation to glide over it unhindered: old snow fills all the unevenness of the soil, bends the bushes to the ground, forming a perfectly smooth surface (the larger its layer, the less rough obstacles that can stop snow from falling).

The most dangerous periods when snow falls are considered winter and spring (about 95% of cases are recorded at this time). Snowfall is possible at any time of the day, but more often this event occurs during the day. The occurrence of landslides and snow avalanches is primarily influenced by:

  • Snowfall or concentration huge amount snow on mountain slopes;
  • Weak cohesive force between new snow and underlying surface;
  • Warming and rain, resulting in a slippery layer between the snowfall and the underlying surface;
  • Earthquakes;
  • Sudden change in temperature regime (a sharp cold snap after an unexpected warming, which makes it possible for fresh snow to slide comfortably over the formed ice);
  • Acoustic, mechanical and wind effects (sometimes a scream or a pop is enough to set the snow in motion).

Sweeping everything out of the way

Freshly fallen snow precipitation is held on the slope due to the friction force, the magnitude of which depends primarily on the angle of the slope and the moisture content of the snow. The collapse begins after the pressure of the snow mass begins to exceed the force of friction, as a result of which the snow comes into a state of unstable equilibrium.

As soon as the avalanche begins its movement, an air pre-avalanche wave is formed, which clears the way for the avalanche, destroying buildings, filling up roads and paths.


Before the snow falls, a dull sound is heard high in the mountains, after which a huge cloud of snow rushes down from the top at high speed, taking with it everything that comes in its way. It rushes without stopping, gradually gaining momentum, and stops no sooner than it reaches the bottom of the valley. After that, a huge layer of snow dust rises high into the sky, forming a continuous fog. When the snow dust descends, dense piles of snow open before your eyes, in the middle of which you can see branches, the remains of trees, and stone blocks.

Why are avalanches dangerous?

According to statistics, it is snowfall that causes fifty percent of accidents in the mountains, and often causes the death of climbers, snowboarders, skiers. An avalanche going down can simply throw a person off the slope, because of which he can break during the fall, or fall asleep with such a thick layer of snow and cause death from cold and lack of oxygen.

A snow fall is dangerous because of its mass, often several hundred tons, and therefore, covering a person, often leads to his suffocation or death from pain shock caused by a broken bone. In order to warn people about the approaching danger, a special commission developed a system for classifying the risks of avalanches, the levels of which are indicated by flags and hung out at ski resorts and resorts:

  • The first level (minimum) - the snow is stable, so a collapse is possible only as a result of a strong impact on the snow masses on very steep slopes.
  • The second level (limited) - the snow on most slopes is stable, but in some places it is a little unstable, but, as in the first case, large avalanches will occur only due to a strong impact on the snow masses;
  • The third level (middle) - on steep slopes, the snow layer is weakly or moderately stable, and therefore an avalanche can form with a slight impact (sometimes an unexpected large snowfall is possible);
  • Fourth (high) - the snow is unstable on almost all slopes and the avalanche descends even with a very weak impact on the snow masses, while a large number of medium and large unexpected avalanches may occur.
  • Fifth level (very high) - the probability of a huge number of large collapses and snow avalanches, even on non-steep slopes, is extremely high.

Safety

In order to avoid death and not be buried under a thick layer of snow, every person who is going to the mountains to rest while there is snow there must learn the basic rules of behavior when a deadly stream descends.

If during your stay at the base an avalanche warning was announced, it is advisable to refrain from hiking in the mountains. If there was no warning, then before leaving the base and hitting the road, you need to take into account the forecast of the risk of the probability of snow melting, and also find out as much as possible about the mountains in which the risk of avalanches is maximum and avoid dangerous slopes (this simple rule of behavior is quite capable of saving life).

If heavy snowfalls were recorded before going out into the mountains, it is better to postpone the trip for two or three days and wait for the snow to fall, and in the absence of avalanches, wait until it settles. It is also very important not to go to the mountains alone or together: it is advisable to stay in a group. This will always provide insurance for an avalanche, for example, if the group members are tied with an avalanche tape, this will make it possible to detect a satellite covered with snow.

Before going out into the mountains, it is advisable to take an avalanche transceiver with you, which will make it possible to find the person caught in the avalanche.

It is very important not to forget to take with you mobile phone(he has already saved the life of more than one person). It’s also a good idea to take special avalanche backpacks, which provide a system of inflatable pillows that make it possible for a person caught in an avalanche to “surface”.

In the mountains, you need to move only along the roads and paved paths of the valleys and along the ridges of the mountains, while it is very important to remember that you cannot go onto steep snow-covered slopes, cross them across or move in a zigzag. It is also forbidden to step on snow ledges, which are accumulations of dense snow in the form of a canopy on the leeward side of a sharp ridge (they may well suddenly collapse and cause an avalanche).

If it is not possible to get around a steep slope, before you overcome it, you need to make sure that the snow cover is stable. If he begins to sag under his feet and at the same time begins to make a hissing sound, you need to go back and look for another way: the likelihood of an avalanche is high.

Trapped in snow

If the avalanche has broken high and there is time to do something, it is very important to remember one of the basic rules of behavior when an avalanche rushes at you: to leave the path of the rushing stream to a safe place, you need to move not down, but horizontally. You can also hide behind a ledge, preferably in a cave, or climb onto a rise, a stable rock, or a sturdy tree.

In no case should you hide behind young trees, as the snow can break them.

If it so happened that you couldn’t get away from the avalanche, one of the rules of conduct says that you need to immediately get rid of all the things that will drag you into the rushing stream and hinder movement: from a backpack, skis, sticks, ice ax. It is necessary to immediately begin to sharply make your way to the edge of the stream, doing everything possible to stay at the top, and if possible, catch on a tree, stone, bush.

If the snow is still covered with the head, then the nose and mouth must be covered with a scarf or hat so that snow does not get there. Then you need to group: turning in the direction of the snow flow, take a horizontal position and pull your knees to your stomach. After that, with circular rotations of the head, do not forget to form as much free space as possible in front of the face.


As soon as the avalanche stops, you need to try to get out on your own or at least push your hand up so that the rescuers notice it. It is useless to scream, being under the snow cover, since the sound is transmitted very weakly, therefore, such efforts only weaken the forces (it is necessary to give sound signals only when the steps of the rescuers are heard).

It is important not to forget the rules of behavior under the snow: you need to remain calm and in no case panic (screams and senseless movements will deprive you of strength, heat and oxygen). Do not forget to move, otherwise a person sandwiched in the thickness of the snow will simply freeze, for the same reason you need to do everything not to fall asleep. The main thing is to believe: there are cases when living people were found under the snow cover even on the thirteenth day.

Avalanches form with sufficient snow accumulation and on treeless slopes with a steepness of 15 to 50°. With a steepness of more than 50 °, the snow simply crumbles, and the conditions for the formation of a snow mass do not arise. The optimal situations for the occurrence of avalanches are formed on snow-covered slopes with a steepness of 30 to 40 °. There, avalanches descend when the layer of freshly fallen snow reaches 30 cm, and for old (stale) snow, a cover 70 cm thick is required. increases the likelihood of avalanches. Shrub vegetation is not an obstacle to the descent. The best condition for starting the movement of the snow mass and gaining a certain speed by it is the length of the open slope from 100 to 500 m. Much depends on the intensity of the snowfall. If 0.5 m of snow falls in 2-3 days, then this usually does not cause concern, but if the same amount falls in 10-12 hours, then the descent is quite possible. In most cases, the snowfall intensity of 2-3 cm/h is close to critical.

The wind is also important. So, with a strong wind, an increase of 10 - 15 cm is enough, as an avalanche can already occur. The average critical wind speed is about 7-8 m/s.

One of the most important factors influencing the formation of avalanches is temperature. In winter, with relatively warm weather, when the temperature is close to zero, the instability of the snow cover increases greatly, but quickly passes (either avalanches come down or the snow settles). As the temperature drops, the periods of avalanche danger become longer. In the spring, with warming, the likelihood of wet avalanches descending increases. damaging ability different. An avalanche of 10 m 3 is already a danger to humans and light equipment. Large ones are able to destroy capital engineering structures, form difficult or insurmountable blockages on transport routes.

Speed ​​is one of the main characteristics of a moving avalanche. In some cases, it can reach 100 m/s. The release range is important for assessing the possibility of hitting objects located in avalanche zones. Distinguish between the maximum range of the release and the most probable, or long-term average.

The most probable range of release is determined directly on the ground. It is evaluated if it is necessary to place structures in the avalanche zone for a long period. It coincides with the boundary of the avalanche source fan. The frequency of avalanches is an important temporal characteristic of avalanche activity. Distinguish between the average long-term and intra-annual recurrence of the descent. The first is defined as the frequency of avalanche formation on average over multi-year period. Intra-annual frequency is the frequency of descent during the winter and spring periods. In some areas, avalanches can descend 15-20 times a year.

The density of avalanche snow is one of the most important physical parameters, which determines the impact force of the snow mass, labor costs for its clearing or the ability to move along it. It is for dry snow avalanches 200 - 400 kg / m 3 for wet - 300 - 800 kg / m 3.

An important parameter, especially when organizing and conducting rescue operations, is the height of the avalanche flow, most often reaching 10-15 m.

The potential period of avalanche formation is the time interval between the first and last avalanches. This characteristic must be taken into account when planning the mode of activity of people in a dangerous area. avalanche snow destructive elemental

It is also necessary to know the number and area of ​​avalanche centers, the dates of the beginning and end of the avalanche period. These settings are different for each region. In Russia, most often natural disasters occur on the Kola Peninsula, the Urals, the North Caucasus, in the south of Western and Eastern Siberia, the Far East. Avalanches on Sakhalin have their own characteristics. There they cover all altitudinal zones - from sea level to mountain peaks. Descending from a height of 100 - 800 m, they cause frequent interruptions in the movement of trains on the Yuzhno-Sakhalin railway. The vast majority in mountainous areas avalanches descend annually, and sometimes several times a year. How are they classified?

To assess the probability of avalanches of freshly fallen and snowstorms, 10 main avalanche-forming factors are used (Inzhenernaya Geologiya…, 2013).

1. Height of old snow. Snow first fills the unevenness on the slope, and only after that can a flat, smooth surface appear, contributing to the sliding of new layers of snow cover. Therefore than more height old snow before the start of snowfall, the greater the likelihood of avalanches.

2. Condition of old snow and its surface. The nature of the snow surface affects the grip of the chewed snow with the old one. The smooth surface of wind-driven snow slabs or ice crust favor avalanches. The presence of layers and interlayers of deep frost is especially predisposing to avalanche formation. A rough surface, wind sastrugi, porous crusts from rain, on the contrary, reduce the possibility of avalanche formation.

3. Height of freshly fallen or blizzard-deposited snow. An increase in the height of snow cover is one of the most important factors in avalanche formation. The amount of snowfall is often used as an indicator of potential avalanche danger.

4. View of freshly fallen snow. The type of solid precipitation that occurs affects the mechanical properties of the snow cover and its adhesion to old snow. Thus, when prismatic and needle-shaped crystals or star-shaped crystals fall out in frosty calm weather, a loose snow cover is formed, characterized by low adhesion. The greatest probability of avalanche formation occurs when a cover is formed from freshly fallen fluffy and dry fine-grained snow.

5. Density of freshly fallen snow. The highest probability of avalanche formation is observed when a snow cover of low density is formed - less than 100 kg / m3. An increase in snow density reduces the likelihood of avalanches, but this rule does not apply to snow slabs formed during snowstorms.

6. Snowfall intensity (speed of snow deposition). At low snowfall intensity, the decrease in the stability index of the snow cover on the slope as a result of an increase in shear forces is compensated by an increase in stability due to an increase in adhesion and friction coefficient during snow compaction. As the speed of snow deposition increases, the effect of an increase in its mass prevails over the effect of its compaction, and creates conditions for a decrease in the stability of the snow cover and the formation of avalanches.

7. The amount and intensity of precipitation - a factor characterizing the increment in the mass of snow per unit area of ​​the horizontal projection of the slope, including taking into account liquid precipitation and snowstorms.

8. Snow settling. The process of compaction and settling of the falling snow increases its grip and coefficient internal friction and this contributes to the stability of the snow cover.

9. Wind. Wind transport leads to the redistribution of snow cover, the formation of hard crusts, snow slabs and puffs. The wind forms snow cornices and below them - accumulations of loose snow. A strong wind creates a suction of air from the snow mass, which contributes to the migration of water vapor and loosening of the lower layers of snow. In the processes of avalanche formation, the wind plays important role, especially as a factor of blizzard snow transfer.

10. Temperature. The effect of temperature on avalanche formation is multifaceted. The air temperature affects the type of falling solid precipitation particles, the formation, compaction and temperature regime of the snow cover. The difference in the temperature of the snow cover in depth is also determined by the processes of temperature-gradient metamorphism. A rapid decrease in air temperature can lead to the formation of temperature cracks in the rupture of the snow layer and the occurrence of avalanches.

To active methods of avalanche protection include activities aimed at initiating avalanches, so that the consequences of this are minimal. For these purposes, shooting from artillery piece(moreover, both with a projectile - in the area where a dangerous snow mass is located, and with a blank shot, in order to create an acoustic effect, leading to a deliberate avalanche). The methods of simple "cutting" of snow masses with skis and the collapse of snow peaks have long been used, but these methods require good skills and are very dangerous. The most modern way to prevent the negative consequences of avalanches - active dynamic anti-avalanche protection, which is a device located in places of the greatest avalanche formation and remotely controlled, which allows you to influence the snow masses in order to artificially release an avalanche, using compressed air or explosions of a gas-air mixture.

Passive avalanche protection measures are aimed at keeping snow on the slope and preventing avalanches from coming down, or at directing avalanches that have come down in a safe direction. Such measures include the construction of avalanche barriers, flumes, avalanche cutters and dams on the slopes (Sadakov, 2009). On linear objects, such as automobile or railways, construct avalanche galleries.

Mountains are undoubtedly one of the most beautiful and fascinating panoramas of the Earth. Many strive to conquer the majestic peaks, not fully realizing how harsh such beauty is. That is why, deciding on such a brave step, extreme people face difficulties in all their manifestations.

The mountains are a rather dangerous and complex terrain, in the expanses of which there is a constant mechanism of gravity, so the destroyed rocks move and form plains. Thus, the mountains eventually turn into small hills.

In the mountains, danger can always await, so you need to undergo special training and be able to act.

Definition of Avalanches

snow avalanches are one of the most devastating, dangerous destructive phenomena of nature.

An avalanche is a rapid, sudden, minute process of moving snow with ice, occurring under the influence of gravity, the water cycle and many other atmospheric and natural factors. Such a phenomenon most often occurs in the winter/spring period, much less often in summer/autumn, mainly at high altitudes.

It is always worth remembering that the avalanche is primarily a harbinger of weather conditions. Hiking in the mountains in bad weather: snowfall, rain, strong wind- quite dangerous.

Most often, an avalanche occurs, lasting about a minute, while passing a distance of about 200–300 meters. It is extremely rare to hide or run away from an avalanche, and only if it became known about it at least 200–300 meters away.

The avalanche mechanism consists of a sloping slope, an avalanche body and gravity.

Sloping slope

The level of the slope, the roughness of its surface greatly affect the avalanche risk.

A slope of 45–60° is usually not dangerous, as it gradually unloads during snowfalls. Despite this, such places under certain weather conditions can create avalanche accumulations.

Snow will almost always fall from a slope of 60–65°, and this snow can linger on convex sections, creating dangerous blowouts.

Slope 90 ° - the collapse is a real snow avalanche.

avalanche body

Formed from accumulations of snow during an avalanche, it can crumble, roll, fly, flow. The type of movement directly depends on the roughness of the lower surface, the type of snow accumulation, and swiftness.

Types of avalanches according to the movement of snow accumulations are divided:

  • to streaming;
  • cloudy;
  • complex.

Gravity

It acts on the body on the surface of the Earth, is directed vertically downwards, being the main mobile force that contributes to the movement of snow accumulations along the slope to the foot.

Factors affecting the occurrence of an avalanche:

  • type of matter composition - snow, ice, snow + ice;
  • connectivity - loose, monolithic, reservoir;
  • density - dense, medium density, low density;
  • temperature - low, medium, high;
  • thickness - thin layer, medium, thick.

General classification of avalanches

Avalanches of powdered, dry recent snow

The convergence of such an avalanche usually occurs during heavy snowfall or immediately after it.

Powder snow is called fresh, light, fluffy snow, consisting of tiny snow flakes and crystals. The strength of snow is determined by the rate of increase in its height, the strength of the connection with the ground or previously fallen snow. It has a fairly high fluidity, which makes it possible to easily flow around a variety of obstacles. IN different occasions can reach speeds of 100-300 km / h.

Avalanches created by snowstorms

Such a convergence is the result of the transfer of snow by a blizzard. Thus, the snow is transferred to the mountain slopes and negative landforms.

Avalanches of dense dry powder snow

They arise from snow a week old or more, which during this time is pressed, becomes much denser than freshly fallen. Such an avalanche moves more slowly, partially turning into a cloud.

landslide avalanches

They grow after the collapse of snow cornice blocks, which set in motion a large amount of snow.

Dust avalanches

An avalanche is characterized by a huge cloud or a thick layer of snow on trees and rocks. Created when dry, powdery recent snow melts. A dust avalanche sometimes reaches a speed of 400 km/h. Risk factors are: snow dust, strong shock wave.

Formation avalanches

They arise through the descent of layered snow, reach a speed of 200 km / h. Of all the snow avalanches are the most dangerous.

Avalanches from hard sheet snow

A stream is formed by the descent of solid layers of snow over a weak, loose layer of snow. They consist mainly of flat snow blocks resulting from the destruction of dense formations.

Soft plastic avalanches

Snow flow is formed by the descent of a soft layer of snow on the underlying surface. This type of avalanche is created from wet, settled, dense or moderately cohesive snow.

Avalanches of monolithic ice and ice-snow formations

At the end of winter, snow deposits remain, which, under the influence of external factors, become much heavier, turning into firn, eventually turning into ice.

Firn is snow cemented by frozen water. It is formed during temperature drops or fluctuations.

Complex avalanches

Consist of several parts:

  • flying cloud of dry snow;
  • a dense stream of formation, loose snow.

They arise after a thaw or a sharp cold snap, which is the result of the accumulation of snow, its separation, thereby forming a complex avalanche. This type of avalanche has catastrophic consequences and can destroy a mountain settlement.

Avalanches are wet

Formed from snow accumulations with the presence of bound water. Occur during the period of accumulation of moisture by snow masses, which occurs during precipitation and thaw.

Avalanches are wet

They arise due to the presence of unbound water in snow accumulations. Appear during a thaw with rain and warm wind. They can also occur by sliding a wet layer of snow over the surface of old snow.

Mudflow-like avalanches

They arise from snow formations with a large amount of moisture, the driving mass of which floats in a large volume of unbound water. They are the result of long thaws or rains, as a result of which the snow cover has a large excess of water.

The presented types of avalanches are quite dangerous, fast-moving flows, so you should not think that some are safer than others. The basic safety rules must always be followed.

Avalanche safety

The term avalanche safety refers to a set of actions aimed at protecting and eliminating the tragic consequences of avalanches.

As practice shows, in most accidents the extreme people themselves are to blame, who, without calculating their own strength, themselves violate the integrity and stability of the slopes. Unfortunately, there are deaths every year.

The main rule for the safe crossing of mountain ranges is the full knowledge of the passable territory, with all the dangers and obstacles, so that in an emergency you can safely, carefully leave the dangerous section of the path.

People going to the mountains, elementary rules avalanche safety, be able to use avalanche equipment, otherwise the probability of falling under a snow blockage and death is very high. The main equipment is avalanche shovels, beepers, avalanche probes, float backpack, maps, medical equipment.

Before going to the mountains, it will be useful to take courses on rescue operations during a collapse, first aid, making the right decisions to save lives. Also milestone is a training of the psyche and ways to overcome stress. This can be learned in courses on working out techniques for saving people or yourself.

If a person is a beginner, it will be useful to read books about avalanche safety, which describe different situations, moments, stages of overcoming them. For a better understanding of avalanches the best option will personal experience obtained in the mountains in the presence of an experienced teacher.

Avalanche safety basics:

  • mental attitude and preparation;
  • obligatory visit to the doctor;
  • listening to an avalanche safety briefing;
  • taking with you a sufficient amount of food, small in volume, a spare pair of clothes, shoes;
  • careful study of the route, upcoming weather conditions;
  • taking a first aid kit, flashlight, compass, equipment on a hike;
  • departure to the mountains with an experienced leader;
  • studying information about avalanches in order to have an idea of ​​the degrees of avalanche safety during a collapse.

A list of avalanche equipment, which you need to be able to work with confidently, quickly, for own security and rescuing the victims

  • victim search tools: transmitter, avalanche ball, beeper, radar, avalanche shovel, avalanche probe, other necessary equipment;
  • tools for checking snow flooring: saw, thermometer, snow density gauge and others;
  • tools for rescuing victims: backpacks with inflatable pillows, avalanche breathing apparatus;
  • tools for transporting victims, as well as medical equipment: bags, stretchers, backpacks.

Avalanche slopes: precautions

In order to avoid getting into an avalanche, or if there is a high probability of an avalanche situation, you need to know a few important rules on avalanche safety and prevention.

  • move on safe slopes;
  • do not go to the mountains without a compass, know the basics of the direction of the winds;
  • move along elevated places, ridges that are more stable;
  • avoid slopes with snow cornices hanging over them;
  • return along the same road that went ahead;
  • monitor the top layer of the slope;
  • do tests on the strength of the snow cover;
  • it is good and reliable to fix the insurance on the slope, otherwise the avalanche can drag a person with it;
  • take on the road spare batteries for the phone and a flashlight, and also have in the memory of the mobile phone the numbers of all nearby rescue services.

If a group or a certain number of people still find themselves under an avalanche, you need to call rescuers, immediately starting the search on your own. In such a situation, the most necessary tools there will be an avalanche probe, a beeper, a shovel.

Every person who goes to the mountains should have an avalanche probe. This tool performs the function of sounding snow during search operations. It is a dismantled rod, two to three meters long. On security courses obligatory item is the assembly of an avalanche probe in order to assemble it in the shortest possible time when creating an extreme situation.

An avalanche shovel is indispensable when searching for victims, it is necessary for digging snow. It is more effective when combined with an avalanche probe.

A beeper is a radio transmitter that can be used to track a person covered in snow.

Only with coordinated, quick actions can a comrade be saved. After a thorough briefing on avalanche safety, a person will be mentally and physically ready to help others.

As a result, I would like to emphasize that hiking in the mountains cannot be carried out in bad weather, in the evening or at night, when crossing a dangerous area, it is necessary to use rope insurance, be sure to have beepers, flashlights, avalanche shovels and avalanche probes in the arsenal. Some part of these instruments must necessarily have a length of 3-4 m.

Observing all the rules, following the instructions, a person will protect himself from disastrous consequences and return home safely.

Write to us if the article was useful.

The materials of the site www.snowway.ru and from other open sources were used.

Avalanches. Every year, many people die under them, either because they neglect the danger, or because little is known about avalanches.

Many of us do not take the threat of avalanches seriously until someone is killed or injured in one. The sad fact is that people caught in an avalanche usually provoke them themselves. Skiers cut slopes, climbers go during avalanche times. Moreover, the victims are often professionals in their field, but neglect the avalanche danger. This article provides basic knowledge about avalanches.

Avalanches.

Potential Threats

An avalanche can move at a speed of 200 kilometers per hour. Such a force can smear you against trees and stones, grind you against rocks, make porridge from your insides and pierce you with your own skis or snowboard. About one third of all avalanche victims die due to injuries.

If you have not been injured by an avalanche, you will have to struggle with a mass of snow, the density of concrete, which squeezes your body. The avalanche, which began as snow dust, heats up as it moves downhill from friction on the slope, thaws a little and then freezes tightly around your body. All this mass is enough to squeeze all the air out of your lungs.

If you manage to create an air pocket around you before the snow settles, you have a good chance of surviving. If you and your friends have an avalanche transmitter and know how to use it, then the chances of survival are even greater. However, this is where the race against time begins. Most people are not able to survive under an avalanche for more than 30 minutes (Black Diamond AvaLung backpacks can increase this time to one hour), so it makes sense to buy and learn how to use avalanche transmitters. For lovers of winter freeride, a necessary thing. About 70% of avalanche victims die from suffocation.

The best defense against avalanches is, of course, knowledge of avalanche conditions and slopes, as well as avoiding dangerous situations.

Loose avalanches.

Such avalanches form when there is little or no adhesion to the snow cover. As a rule, such avalanches begin from one point either on the slope surface or close to it. Such avalanches gain a large snow mass and momentum while moving down the slope, often forming a triangular path behind them. The causes of such avalanches may be blocks of snow falling on the slope from the rocks above or melting snow cover.

Such avalanches occur on dry and wet snow, descend both in winter and in summer. Winter loose avalanches usually occur during or after a snowfall. In more warm time year, the cause of wet loose avalanches is snow or melt water. These avalanches are dangerous both in winter and in summer.

Plastic avalanches.

These avalanches are much more dangerous. Sheet avalanches form when a single layer of snow slides off the bottom layer and rushes down a slope. Most freeriders get into such avalanches.

They are caused by snowfalls and strong winds that deposit layers of snow that change over time. Some layers are deposited and held together, while others, on the contrary, are weakened. Weak layers are often granular or composed of very light snow (powder) so that other layers cannot adhere to them.

An avalanche occurs when the top layer, called the “board,” is not sufficiently bonded to the underlying layer and is set in motion by some external factor, usually a skier or climber. Unlike unconsolidated avalanches, which start from a single point, sheet avalanches grow deeper and wider, usually along a break line at the top of a slope.

Avalanche release on Cheget:

Factors contributing to the descent of avalanches.

Locality.

Slope steepness: pay attention to the steepness of the slope when you ride or climb. Avalanches often occur on slopes steep in 30-45 degrees.

Slope side: in winter, the southern slopes are much more stable than the northern slopes, as the Sun heats and compacts the snow. Unstable layers of "deep frost", dry, icy snow that does not adhere to adjacent layers, are most often found on the northern slopes. So be careful when you see the tempting northern slope with excellent powder, for they are more dangerous than the southern slopes, in view of the fact that they do not receive enough solar heat to compact the snow over the winter. At the same time, in spring and summer, the southern slopes melt more strongly, which leads to dangerous wet avalanches. The warmer weather this time of year hardens the snow on the northern slopes, making them safer.

Terrain Threats: Snow cover is most often unstable on convex slopes, rock ledges, boulders or trees where the snow cover is interrupted, on lee slopes or under eaves. It is best to bypass bowls, circuses and pits, where snow can accumulate after an avalanche (avalanche discharges). Steep, narrow couloirs (or ravines) usually accumulate a lot of snow and pose a great danger to hikers and skiers caught in them. Often, there is no escape from such places, due to the steep side slopes, so that in the event of an avalanche, there is nowhere to run.

Weather

Precipitation: snow is least stable after snowfalls or rains. A large amount of snow falling in a short period of time is a sign of avalanche danger. Heavy snowfall, especially wet or dense snow falling on powder, forms unstable layers in the snowpack. Rain seeps in and heats the bottom layers of the snowpack and also reduces friction between the layers, making them less stable. After a heavy snowfall, you need to wait at least two days before going to avalanche areas.

Wind: Another indicator of snow cover instability is wind. Often, strong winds carry surface snow from one slope to another part of the ridge, where the snow descends to form an avalanche. Pay attention to the intensity and direction of the wind during the day.

Temperature: a large number of problems with snow cover are caused by temperature fluctuations. The formation of snow crystals can change in case of temperature difference between the surface and overlying layers, different layers in the center of the cover, and even between the air temperature and the upper snow layer. A particularly dangerous snow crystal, due to its inability to bond with other crystals, is "hoarfrost".


Deep frost ("sugar snow"), due to its similarity to granulated sugar, can be located at any depth or several depths of deep snow cover. Often a sharp increase in temperature leads to wet avalanches, especially in spring, so be careful when it gets warm in the mountains.

Snow cover

Snowfalls come one after another throughout the winter. Temperature changes cause metamorphoses of snow crystals. If the composition of the snow remains the same, then the snow cover is uniform and stable. Snow becomes dangerous and unstable when layers form inside the snow cover. different snow. To every freerider it is essential to check snow layers for stability, especially on slopes of 30-45 degrees.

How to test a slope for avalanche risk:

Human factor

While terrain, weather, and snow cover play a big role in triggering avalanches, it's important to remember that selfishness, emotions, and herd mentality can seriously cloud your judgment and lead you to make rash decisions. In fact, according to a recent survey of Canadian avalanche workers, those surveyed cited 'human error' and 'poor site selection' as the main causes of accidents caused by avalanches. Most avalanches are caused by humans!

Common mistakes in decision making:

  • Familiar places: it is most likely that you will take risks in a place you are familiar with. Conditions, however, can change from minute to minute, so treat any area as if you were seeing it for the first time.
  • OK: encouragement from the group can put a lot of pressure on you. "Yes, everything will be fine, relax!". Even if you feel something is wrong, you may be taking unnecessary risks to please the group.
  • Reach the place at any cost: if you want too much to get to your destination, you can act contrary to your common sense and ignore the signs of danger, concentrating only on their goals. Foreign climbers call this phenomenon "summit fever".
  • "We have an expert": you imply that there is someone else in your group with more experience than you. Think you do, based on what this person was in this place before you or he went through some special education. Better to ask than to guess.
  • Existing trails: you can feel safe because you see a trodden path ahead of you. In our mountains, once I walked along a seemingly excellent path, but I felt that the slope under the path was not very reliable. Just because someone else has been here before you doesn't mean it's safe to walk around.
  • "Virgin Fever": You can turn a blind eye to signs of avalanche danger when you have fresh, deep, and untouched snow in front of you. Don't be tempted!
  • "Others have passed!": it's very easy to give in to the "herd instinct" and head off onto a dangerous slope when other people have already passed in front of you. Always assess the situation as if you were alone. Tell me if you feel something is wrong.

There are several classifications of avalanches based on different signs: type of snow (loose or dense), water content in snow, nature of movement, sliding surface, path morphology.

However, the general classification of avalanches should reflect their most significant features and serve the practical purposes of organizing protection against avalanches. These requirements are best met by two approaches to the division of avalanches into main types. The first genetic - comes from taking into account the causes of avalanches, which were mentioned above; its value lies in the possibility of developing a forecast of the onset of an avalanche danger. The second approach is based on taking into account the relief of the snow-collecting basin and the path of the avalanche. This principle of subdivision of avalanche vehicles makes it possible to calculate the volumes and ranges of avalanche releases, i.e., it is necessary when mapping avalanche-prone areas. In this tutorial, we will consider the first approach to the classification of avalanches.

Genetic classification avalanches, most fully developed by the Soviet researcher VN Akkuratov, includes the following classes and types of avalanches.

I. Class of dry (cold) avalanches.

Such avalanches usually consist of dry snow; descend mainly in winter; exit paths are not strictly limited - they can go down a flat slope and partially through the air. They have a maximum speed, they can form an air wave. The dry class includes the following types avalanches:

1. Avalanches from freshly fallen snow. Such avalanches occur due to overloading of slopes during prolonged snowfalls. For avalanches, 0.3-0.5 m of fresh snow is enough. In snowy areas of temperate climate this type of avalanches is the main one.

2. Snowstorm avalanches. The reason for their occurrence is the high growth rate of the gravity component on the slope. This is the most characteristic type avalanches for areas with a moderately cold climate and a stormy wind regime.

3. Avalanches associated with the recrystallization of snow and the formation of layers of deep frost (cohesion forces in which are weakened). Usually rare but powerful avalanches.

4. Avalanches of temperature reduction of snow cover. These avalanches occur as a result of a sharp drop in air temperature. Also a rare type of avalanches.

II. The class of wet (warm) avalanches.

Such avalanches are formed from wet or wet snow; they descend mainly in the spring; exit paths are usually constant; movement is carried out along the lower horizons of snow or on the ground; the speed of movement is less than that of dry avalanches; the impact is mainly due to the pressure of heavy (water-soaked) masses of snow.

1. Avalanches resulting from radiation thaws. These are low-power avalanches of the southern (sunny) slopes.

2. Avalanches associated with thaws and spring snowmelt usually consist of wet, less often wet snow. The sliding surface is usually the interface between snow layers, i.e. avalanches belong to the category of reservoir.

3. Ground avalanches are formed in the spring from wet snow completely saturated with water, due to prolonged thaws and rains, or during rapid snowmelt during dryers. They always descend along certain paths, therefore, as a rule, they have names. They carry a significant amount of detrital material. The roar of these avalanches is called "avalanche thunder" by the inhabitants of the Alps. The most destructive in the class of wet avalanches.

Avalanches are one of the most widespread and dangerous natural phenomena mountainous countries. Avalanches are mentioned in the writings of ancient writers who lived more than 2000 years ago. The ancient Greek historian Polybius (201-120 BC) writes about losses from avalanches during the passage of Hannibal's troops through the Alps (218 BC). The ancient Roman geographer Strabo (63 BC - 20 AD) wrote about the avalanche danger that awaits the traveler in the Alps and the Caucasus.

In January 1951, the entire Alpine mountain range, about 700 km long and up to 150 km wide, was in the zone of avalanche disasters. The snowfall, accompanied by snowstorms, continued in many areas for seven days and ended with a sharp warming. The amount of snowfall in some places exceeded the annual precipitation rate by 2-3 times and reached 2-3 m. The slopes turned out to be overloaded with snow, and mass avalanches began. The entire transport network of the Alps was disrupted - highways and railways were destroyed in places or littered and temporarily closed. Avalanches descended in places where many generations of inhabitants did not know them. Hotel buildings were destroyed protected forests. The season was called "Winter of Terror".

In February 1999, an avalanche weighing 170 thousand tons completely destroyed the village of Galtur in Austria, causing the death of 30 people, and in early March 2012, a series of avalanches in Afghanistan destroyed residential buildings, causing the death of at least 100 people.

In Russia, snow avalanches are common in the mountainous regions of the Caucasus, the Urals, Eastern and Western Siberia, the Far East, and Sakhalin.

Today, many countries have accumulated significant experience in avalanche protection.

Complex of anti-avalanche measures consists of two main categories - preventive and engineering.

Preventive actions are reduced to a warning of an avalanche danger and its elimination by artificial dropping. To prevent avalanche danger, maps of avalanche zones and a forecast of the time of avalanches are compiled.

Preventive measures also include warning the population about the onset of avalanche periods.

Artificial dropping of avalanches is carried out by mortars or undermining the avalanche area with explosives. Avalanche collections are also fired for control, in order to check the stability of the snow on the slope.

Engineering activities are usually used to protect settlements and capital structures from avalanches. To do this, tunnels, galleries, sheds are being built. Typically, these structures are used to cover individual sections of railways and highways passing in the mountains.

For many years, structures have been erected that change the path of the avalanche, reduce the speed and range of the release - avalanche cutters, wedges, guide walls, wallpaper dams, etc.

They partially extinguish the energy of the avalanche or divert it from the protected object. Often practiced are such engineering methods as terracing, building slopes with snow-retaining shields. They prevent snow from slipping from avalanches. It's expensive but effective method avalanche control. The protection and restoration of forests on the slopes of the mountains is still considered one of the most important activities in avalanche areas. In the Alps, an avalanche-destroyed forest is immediately restored. The planting of forests is usually combined with the development of slopes with snow-retaining structures.

A dense forest serves as a natural protection against avalanches. It prevents the redistribution of snow by the wind, divides the snow cover into separate sections. In Switzerland, a law prohibiting logging on mountain slopes has existed since the 14th century. The destruction of forests on the slopes of the mountains always stimulates avalanche activity.

Mudflows

Mud flow - a turbulent mud or mud-stone stream, consisting of a mixture of water and debris rocks, suddenly arising in the basins of small mountain rivers. Mudflows pose a threat to settlements, railways and roads and other structures located on their way.

The immediate causes of mudflows are showers, intense snowmelt, breakthrough of reservoirs, less often earthquakes, volcanic eruptions.